Correct spacing used between numbers and abbreviations [duplicate]

Solution 1:

I don't get the thing about pounds. if you read it 71 bs it doesn't make sense. However, there should always be a space between the number and the unit to prevent confusion (although I can't see how there would be confusion in then case you stated).

As to the period. The rule of the thumb is that metric measurements should never receive a period and US customary measurements should always receive a period (so, *5 mm. would be incorrect).

I hope this answers your question.

Solution 2:

In our journals we always use a space between the number and the unit of measurement. And we do not use periods after units of measurement, whether metric or not. It is a matter of style, not grammar.